I read the first four books some time ago and thought it was a great series, but it's taken forever for Martin to finish the fifth (which is now supposedly going to be released this summer.)
The HBO adaptation last night was pretty dead-on.
What makes the series so interesting is the way Martin sets up what looks like a pretty standard ho-hum fantasy "good vs. evil" story with all of the usual tropes and stereotypes - - - and then - - he just blows them out of the water.
If you are watching the TV series and haven't read the books, it's still in the "set-up" stage. But stay tuned, and within a week or two, you'll start to see what I mean, when things start going not quite the way you might expect.